Method optimising the quality and integrity of RNA samples from bronchial airway tissues

RNA quality and integrity are key factors that significantly influence the utility of microarray analysis. In this study we sought to optimise RNA isolation techniques for ovine lung tissue that best preserved the quality and quantity of RNA available for subsequent microarray analysis. The primary indices of quality were the optical density (OD), 260/280 and 28S/18S ratios, and the RNA integrity number (RIN) score. Lung cell and tissue samples were harvested either by bronchoscopy under anaesthesia or at necropsy examination, and immediately processed to preserve the RNA. Samples were analysed and electropherograms generated by the Agilent microfluidic capillary electrophoresis BioAnalyzer 2100, allowing calculation of the 28S/18S ratio and the RIN score. Results were compared with visual analysis of the electropherogram to determine the most useful RNA quality metric. We found that the 28S/18S and the OD 260/280 ratios were poorly sensitive for detecting RNA quality and initial RNA concentration, which significantly play a role in ensuring a good quality and integrity of the RNA. Notably the quality of RNA available was dependent on the type of lung tissue (lung tissue vs. bronchial tissue vs. bronchial brush biopsy samples) selected for extraction. The data from this study provides a useful baseline for undertaking a microarray study in relation to obtaining optimal RNA integrity from bronchial tissue samples.